I received the same feedback from other customers. They wondered unknown billing for the storage account even though they do not have any more data in it. It's few amount, but the customer sometimes need to explain what the cost for to their boss.
Eventually, they feel bad because they have never turned the diagnostic on, but it's charged.

Thank you for your patience. This is still under review. We are working on other features that are moving us closer to being able to provide these capabilities, but cannot yet dedicate resources to this feature.
Thanks,
Bridget [MSFT]